Estimation of frequency domain soil parameters of horizontally multilayered earth by using Cole–Cole model based on the parallel genetic algorithm.

A method to estimate frequency domain soil parameters of horizontally multilayered earth is developed. Cole–Cole model of complex conductivity form is adopted to describe the frequency dependence of soil parameters. The estimation of frequency domain soil parameters includes two stages. In the first stage, soil‐layered structure is determined under the DC field by the interpretation of resistivity sounding data. The obtained model parameters in this stage include the DC soil conductivity and thickness of soil layers. In the second stage, Cole–Cole model parameters are estimated based on the soil‐layered model obtained in the first stage. The theoretical formula of complex apparent resistivity is derived from Green's function with considering dynamic‐state field theory. Since dynamic‐state field is considered in the inversion algorithm, this method can be extended into high‐frequency domain. Discrete complex image method is used to calculate Sommerfeld integral quickly. In order to remove electromagnetic (EM) coupling between cables at high frequencies, a new electrode configuration method is proposed. Genetic algorithm is improved by combining with parallel computing. The parallel genetic algorithm is applied to the optimisation of model parameters. [ABSTRACT FROM AUTHOR]